Some Studies on Electric Discharge Machining of Difficult to Machine Materials with Powder Metallurgy Electrodes

Abstract

Electrical discharge machining (EDM) is a well established machining option for processing newlinehard materials with complex geometrical shapes which are extremely difficult-to-machine by newlineconventional machining processes. newline newlineThe purpose of the present work is to correlate the usefulness of PM processed electrodes newlinein imparting desirable material and surface properties to the machined surface by reducing newlinesurface cracks and repairing surfaces. This technique dispenses with the need for supplementary newlineprocessing like coating after EDM thereby reducing the cost of manufacturing. This is explained newlinewith the help of detailed experimental investigation carried out on AISI D2 tool steel and Inconel newline718 super alloy materials using conventional copper electrode and PM processed copper tungsten newline(CuW) electrodes. The machining parameters selected for the study are polarity, electrode type, newlinepeek current (Ip), pulse on time (Ton), duty cycle (and#950;), gap voltage (Vg), retract distance (Rd) and newlineflushing pressure (Fp). The best parameteric settings of the machining parameters have been newlinedetermined through an appropriate orthogonal array experiments for performance measures and newlineresults are analyzed using analysis of variance method. Multi-objective optimization of the newlineperformance parameters has been determined using grey relation theory. Scanning electron newlinemicrograph (SEM) analysis of the machined surfaces shows reduction in surface cracks. Energy newlinedispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis confirmed deposition of newlineelectrode material on the work piece surface causing an appreciable improvement of the surface newlineproperties. XRD analysis confirmed the formation of Fe6W6C phase which resulted in surface newlinecoating of the electric discharge machined surface and an increase in micro hardness of the newlinesurface. newline newline newline